The United States Postal Service (USPS) is seeking to develop a more effective merging system that is responsive to customer needs and culminates in one bundle of mixed letters and flats for each delivery point. The system should accomplish this merging at the step of carrier sequence sorting by merging all elements of the mail stream (letters, flats, periodicals, post cards etc) at the final sorting process.
At present, some of the mail streams arrive at the postal branch offices pre-sorted, and some do not. Generally, even when the mail arrives at the branch already sorted by delivery sequence, postal carriers need to merge multiple streams of mail (often as many as 10) from different mail trays—and for this the postal carriers generally use a manual sorting process. When mail does not arrive at the branch pre-sorted, the carriers spend even more time—several hours—sorting the mail into carrier delivery sequence manually. Often, the carrier on mechanized routes will complete the mail merging while sitting at each post box—merging mail from multiple mail trays on the spot before placing it in the mailbox. This requires carriers to spend substantial time merging and sorting the mail before they can start to deliver it, or else they must complete the merging while they are delivering the mail, thus making the mail delivery process (the last mile) quite inefficient. The instant invention corrects that inefficiency in an automated manner that accommodates not only normal types of mail, but also mail pieces having exceptional physical characteristics.
In 1990, the USPS issued a Request for Proposal for a carrier sequence bar code sorter, type B, a single pass sorter to arrange mail in carrier delivery sequence. To date, 14 years later, no product has been manufactured and delivered to satisfy that need.
The USPS sometimes does delivery sequence sorting at central sorting facilities. The sorting is done there because the equipment required to automate this process is simply too large to fit in the branches. The cost would be prohibitive for the USPS to install such equipment in each branch. Furthermore, sorting centrally is also much more efficient, since the only sorters available today are multiple pass sorters which may include over a hundred bins and may require two or more sort sequences to get the mail in delivery sequence order. However, when the carrier delivery sequence sorting is done centrally, and then sent to branch offices, the carriers usually spend the first two hours of their day re-sorting the mail to correct errors. For many places in the postal network (especially outside the USA), mail is still sorted by the carriers manually, using the old (Ben Franklin) rack of cubbyholes to sort the mail into delivery sequence.
The sorters available today have significant limitations: they are either huge, expensive pieces of equipment with a very large number of bins, and require significant space to operate; or they have a smaller number of bins, but require multiple passes to operate. This multi-pass operation is a very labor-intensive process. So, for example, a sorter with 16 bins, sorting a job with 2000 mail pieces, will require three passes. That means the operator must load the mail, operate the sorter, then unload the mail from each bin and re-load it into the feeder three times! While this results in some time savings compared to manual sorting, the value proposition is limited because of the high labor content. See, for example, U.S. Patent Application Publication No. 20020139726 entitled Single Feed One Pass Mixed Mail Sequencer, filed Apr. 2, 2001.
It is because of the high labor content still required with high speed, multi-pass sorting equipment that the USPS has requested proposals for a single pass system. Unfortunately, even such an automated system single pass system is prone to failure when dealing with mail pieces having exceptional physical characteristics (e.g. due to exceptional bulk or weight).